This invention relates to communication, ranging, and positioning systems and, more particularly, to detecting first-arriving pulses in ultra-wideband communication, ranging, and positioning systems.
Modern communication and radar applications often involve positioning and ranging determinations. These applications typically seek to ascertain the range between two locations, for example between a radar station and a target, between two mobile stations, or between a base station and a mobile station. Other applications seek to determine the absolute or relative position of a target or a location.
Current positioning and ranging techniques suffer from a number of undesirable characteristics. For example, Global Positioning Satellite, or GPS, presently has a resolution limited to a few feet. Moreover, GPS systems rely on expensive, sophisticated satellites orbiting the earth. Thus, ranging and positioning applications that use GPS depend on the availability of the satellites and the signals that the satellites provide. In indoor areas, for example, GPS equipment typically cannot receive satellite signals and, thus, cannot provide reliable ranging and positioning information.
To overcome the shortcomings of GPS systems, other ranging and positioning systems use radar techniques. Radar systems usually transmit a signal that includes a plurality of pulses and, by timing the arrival of a signal reflected from a target, determine the range or position of a target. Those radar systems, like GPS systems, have a limited resolution. To provide improved resolution, some ranging and positioning systems use a single pulse. Proper and reliable operation of those systems, however, depends on their ability to distinguish the first pulse that may include information about the range, position, or both, of a target. Unfortunately, no known reliable techniques exist for detecting the first-arriving pulse and, thus, for determining the range, position, or both, of a target accurately and with improved resolution.
One aspect of the invention contemplates first-arriving pulse (FAP) circuitry for use in ranging, positioning, and communication systems. In one embodiment, FAP detector circuitry according to the invention includes a correlator circuitry configured to correlate a received signal with a template signal to provide an output signal. The FAP detector circuitry also includes a threshold circuitry configured to provide a first-arriving-pulse signal depending on the relative values of the output signal of the correlator circuitry and a threshold signal.
In another embodiment, a radio-frequency apparatus according to the invention includes a radio-frequency circuitry configured to receive a plurality of pulses that result from a transmission of a radio-frequency pulse in a multipath propagation medium. The radio-frequency apparatus also includes a detector circuitry configured to discriminate from a noise floor a first pulse in the plurality of pulses.
In a third embodiment, a communication system according to the invention includes a transmitter circuitry configured to transmit a radio-frequency pulse into a multipath propagation medium and a receiver circuitry configured to receive a plurality of pulses that result from the transmission of the pulse into the multipath propagation medium. The communication system also includes a detector circuitry configured to detect the first pulse of the plurality of pulses.
Another aspect of the invention relates to methods of using FAP circuitry according to the invention in ranging, positioning, and communication systems. In one embodiment, a method of detecting a first-arriving pulse includes correlating a received signal with a template signal to provide a correlation output signal, and comparing the correlation output signal and a threshold signal to provide a first-arriving-pulse signal.
In a second embodiment, a method according to the invention for method of detecting a first pulse includes transmitting a radio-frequency pulse in a multipath propagation medium. The method also includes receiving, by using a radio-frequency circuitry, a plurality of pulses that result from the transmission of the radio-frequency pulse; and discriminating, by using a detector circuitry, a first pulse in the plurality of pulses from a noise floor.